1. Field of the Invention
The present invention relates to methods of using heated gases from thermally diluted combustion to extract and/or process hydrocarbons or carbonaceous materials.
2. Description of Related Art
Global demand for fuel and petroleum products continues to increase. However, discovery of conventional oil reserves has been declining since the mid-1960s. Most remaining hydrocarbon resources are heavier oils or bitumen. This is creating a rapidly growing demand for the recovery and conversion of heavy oil, bitumen, oil sands, and shale oil or kerogen, and for Enhanced Oil Recovery (EOR) of residual higher viscosity oil in conventional reservoirs (herein collectively termed, “heavy hydrocarbons”). Such alternative or heavy hydrocarbon resources have been more difficult, complex, and expensive to convert than conventional petroleum resources.
For example, large deposits of oil sands are found in Alberta Canada, and in the Orinoco region of Venezuela, with total reserves in excess of one trillion barrels of oil equivalent (TBOE) for each. Shallow bitumen deposits are under preliminary development in Alberta. However, most bitumen in place is not considered economical using conventional surface extraction techniques.
The “energy returned on energy invested” (EROEI) strongly influences profitability. EROEI may be as high as 30:1 for conventional petroleum. However, extraction of heavy hydrocarbons is energy intensive, reducing EROEI. Energy use can exceed the energy recovered (i.e., EROEI<1.0) for shale oil recovery. Increasing depletion and maturity of many existing conventional oil fields is generating strong demand for Enhanced Oil Recovery (EOR) and for ways to improve the EROEI for heavy hydrocarbons.
Heavy hydrocarbon extraction commonly uses Steam Assisted Gravity Drainage (hereafter SAGD) to extract bitumen from subsurface oil sands, e.g., as taught by Butler in U.S. Pat. No. 4,344,485, herein incorporated by reference, and subsequent patents such as U.S. Pat. No. 6,230,814, (Nasr, et al.). The Steam Assisted Gas Push (hereinafter SAGP) technique has also been taught, e.g., in U.S. Pat. No. 5,407,009, (Butler, et al.) and U.S. Pat. No. 5,607,016 (Butler, et al.), all herein incorporated by reference. Such methods provide substantial recovery of heavy hydrocarbons.
The SAGD process injects heated steam into buried bitumen formations through horizontally drilled wells. The bitumen is heated by steam to reduce its viscosity and pump a portion of it out of geological formations, e.g., through a second parallel extraction well drilled about 5 m below the first injection well.
Carbon dioxide (hereinafter, CO2) has been used to increase the extraction rate of bitumen and other heavy hydrocarbons as well as other carbonaceous materials such as carbon tetrachloride. The extraction rate can be defined as the rate at which the target material is being removed or delivered in either volume or mass terms. For example, Deo, et al., Industrial Eng. Chem. Res., Vol. 30, No. 3, pp. 532-536 (1991), detailed the specific solubility of CO2 in various bitumens versus temperature and pressure. They reported decreases in viscosity with increasing solvation by CO2. e.g., in Athabasca (Alberta) and Tar Sand Triangle (Utah) bitumens and other heavy hydrocarbons.
In U.S. Pat. No. 5,056,596 (McKay, et al.), herein incorporated by reference, CO2 was dissolved in water at an alkaline pH (e.g., above 10.5) to enhance bitumen recovery rates. However, CO2 is often difficult to obtain near heavy hydrocarbon resources. Long expensive pipelines are typically used to deliver CO2.
The significant decrease in the viscosity of bitumen with increasing solvation by CO2 and/or at increasing temperatures results in higher heavy hydrocarbon extraction efficiencies by delivering CO2. It is desirable to improve delivery of CO2 and steam to enhance the extraction rate of heavy hydrocarbons.
Natural gas is relatively abundant and commonly used to heat heavy hydrocarbons and for power requirements in Western Canada's oil fields and oil sands processing. However, natural gas would be better spent for premium applications requiring very low emissions. A catalytic desulfurization process or “Claus Process”, e.g., as described in U.S. Pat. No. 4,388,288, (Dupin), herein incorporated by reference, is used to remove the sulfur from natural gas, e.g., as hydrogen sulfide, H2S.
Heavy hydrocarbons including bitumen are similarly desulfurized during refining to synthetic crude oil. With high transportation costs, the Northern Alberta market for elemental sulfur appears saturated. Millions of tons of sulfur and/or coke are being stockpiled in the open air in Western Canada. A process to utilize sulfur and/or coke with local raw materials to increase heavy hydrocarbon extraction efficiency is therefore desirable.
For example, to improve extraction, radio-frequency, (hereinafter, “RF” including microwave) heating of hydrocarbons in situ is taught by Supernaw, et al. in U.S. Pat. No. 5,109,927, and by Kinzer in U.S. Pat. No. 7,115,847, both herein incorporated by reference.
Currently known solutions present additional inefficiencies. Among these, latent heat in flue gas is commonly lost to the atmosphere. Also, steam boilers typically require purified water. Water cleanup alone may form 80% of SAGD capital costs. Improvements to the SAGD (or SAGP) process are desirable to increase the economic recovery of heavy hydrocarbons, e.g., by accessing deeper formations in an energy efficient manner, by increasing the percentage of bitumen recoverable from a given depth, by reducing capital costs, and/or reducing the energy costs of hydrocarbon extraction processes.
Water has been used to control the combustion temperature and pollutant emissions in gas turbines for power production and other purposes (e.g., clean water production) as described in U.S. Pat. No. 3,651,461 (Ginter), U.S. Pat. No. 5,743,080 (Ginter), U.S. Pat. No. 5,617,719 (Ginter), U.S. Pat. No. 6,289,666 (Ginter), U.S. patent application Ser. No. 10/763,047 (Hagen et al.), and U.S. patent application Ser. No. 10/763,057 (Hagen et al.), all herein incorporated by reference. Some other related art suggests that adding water during combustion reduces nitrogen oxide (NOx) emissions but increases carbon monoxide (hereinafter, CO) emissions. Ginter and/or Hagen et al. teach methods of delivering water and/or steam which can improve both CO and NOx emissions in the above-mentioned descriptions of VAST (Valued Added Steam Technology) combustion and thermodynamic cycle technologies.
The higher heat capacity and improved control of diluent in VAST combustors or thermogenerators enable more precise control of the combustion temperature and other combustion parameters. Combustion of dirty fuel (e.g., crude oil) has been demonstrated in a VAST wet combustor or thermogenerator. VAST technologies can recycle exhaust heat with steam and/or liquid water, giving substantial improvements in efficiency of wet cycle gas turbines. The use of alternative fuels and more efficient energy use to extract heavy hydrocarbons would be desirable.